Programmably controlled method for grinding end cutting tools and the like

ABSTRACT

Disclosed is a numerically controlled method of broad application but particularly useful for grinding cutting edges and clearance surfaces on cutting tools such as end mills and other similar tools. A programmable numerical servo-motor type control is described. All of the grinding operations are completed at a single station in a series of consecutive grinding operations performed by the same grinding wheel and during which the tool remains in the same work holder. The various cutting edges and clearance surfaces to be ground are both mathematically located and mathematically defined such that the grinding operations may be conducted under numerical control according to optimum wheel speed, feed, position and coolant conditions and with a wide range of independently and simultaneously movable axes. A grinding wheel wear compensation program and a coolant dispensing program are also numerically controlled in coordination with the grinding operations.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a voluntary divisional application of copendingapplication, Ser. No. 810,776, entitled "Programmably Controlled Machineand Method for Grinding End Cutting Tools and the Like", filed June 28,1977, now U.S. Pat. No. 4,115,956, issued Sept. 26, 1978.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to numerically controlled apparatus and methodsfor grinding and particularly as applicable to cutting tools.

2. Description of the Prior Art

While the invention has a broad application to grinding a wide varietyof tools or parts having edges and surfaces whose relative position andshape or form can be defined mathematically, the prior art and theinvention will be discussed primarily in connection with grinding of aball nose end mill as an illustrative case and because of the complexityof such a grinding operation. From such discussion, those skilled in theart will appreciate that many, if not all, of the same basic problemswhich have affected the grinding of a ball nose end mill have alsoaffected the grinding of other tools of equal or simpler complexity andwith respect to which the invention is equally applicable. Also, suchexplanation will indicate how the invention may be applied to othergrinding operations such as encountered in grinding machine parts, e.g.,hydraulic valve spools, cams, crush form dressing rolls, and the like,or as encountered in engraving operations.

End mills in general and ball nose and mills being used forillustration, as now manufactured, are known to have uneven fluteindexing that is not equally spaced and to have varying helix angleswhich can be attributed both to the mill of the flutes as well as todistortion caused in heat treating the metal. Grinding of a ball noseend mill has historically represented a formidable and challengingproblem for which many solutions have been sought over a long period ofyears.

According to early prior art methods of grinding cutting tools, inparticular ball nose end mills, the gash was manually ground resultingin the gash having an undesirable negative rake and also resulting innonuniformity from one flute to the next and from one tool to the next.The O.D. relief was ground using a finger that followed the flutewhereby any imperfections in the flute were carried over and produced inthe O.D. relief. This grinding technique was necessarily a dryoperation, i.e. without a lubricant or coolant fluid, since it was basedupon a "see and hear" technique. By this is meant that the operator hadto see the tool engage the wheel, had to see the finger engage the tooland had to hear the wheel touch the metal. Also, such technique requiredthat the direction of the grinding wheel edge be towards the cuttingedge or surface being ground. This caused heat cracks and burs.

An improvement over the time-honored manual grinding technique isdescribed in commonly-owned U.S. Pat. No. 3,680,263. This patent teachesa grinding machine for grinding the gash in a workpiece having helicalfluting and forming end cutting teeth on such workpiece. The workpieceand grinding wheel are held on independent, manually adjustable supportsystems. The grinding wheel support system provides for no coordinatedaxial movements though the workpiece support system mechanically couplestwo axial movements. The grinding wheel support system, however,provides for independently manual positioning on two linear axes and onerotative axis. The workpiece support system allows independent, manualpositioning on two linear axes in addition to rotative positioning ofthe workpiece itself about its longitudinal axis. Thus while thispatented grinding machine has made provision for relative positioning ofthe tool and grinding wheel with reference to a relatively large numberof reference axes, the complete geometry has not been obtained primarilybecause all of the necessary axis motions for the workpiece and grindingwheel positions were not able to be positioned simultaneously and werenecessarily made manually and by visual observation. It has been foundthat while this was an improvement in the state of the art, the lack ofuniformity from one tool to the next was still a factor and cutters werenot ground to their optimum possibilities nor was it possible to grindthe tools complete with the apparatus described in the patent. Also,there has been the continuing practice of the "see and hear" technique,previously explained.

Other improvements directed to automated grinding of cutting tools areillustrated in U.S. Pat. Nos. 3,680,262; 3,719,459; 3,813,823, and3,816,995. These patents generally teach systems for grinding end millsby machine controlled operations; thus, in some instances, reducing theamount of skill required to duplicate work from one tool to the next.U.S. Pat. Nos. 3,680,262 and 3,813,823, for example, teach a systemhaving three separate stations at which different operations areperformed on the tool under automatic control and with use of a coolant.A first station is the radius/O.D. grinder. The second station is thegasher. The third station is the reliever. Simultaneous movement of tworeference axes is achieved with a cam-follower arrangement. A primarydrawback of this system, however, is that each end mill must be manuallyloaded and unloaded into each of the three stations before grinding iscompleted. The repositioning of the end mill and three different toolholders necessarily results in a nonuniformity among the finished endmills. Furthermore, the three separate grinding machines have to be setup manually for each size cutter and separate grinding wheels, workholders, and the like, must be provided for each machine.

U.S. Pat. No. 3,719,459 also refers to an automatic grinding operation.However, the grinding machine of U.S. Pat. No. 3,719,459 is primarilydirected to grinding the end faces only as distinct from grinding all ofthe required clearance surfaces and cutting edges as with the presentinvention. U.S. Pat. No. 3,816,995 improves on U.S. Pat. No. 3,719,459but the apparatus of both patents is severely restricted in the numberof controlled reference axes and in the number of operations that can becompleted automatically at one station and by inherent limitations ofthe hydraulic-air logic control. Furthermore, all of thepreviously-mentioned prior art is handicapped by the inability to move arelatively large number of reference axes simultaneously andindependently under machine control. In contrast, the present inventionis to a great extent directed to means for providing independent andsimultaneous movement of a large number of reference axes undernumerical control and according to precise, mathematically definedconditions.

A further and more recent improvement in an automatically controlledtool grinder was achieved in the numerically controlled grinder sold andidentified by the trademark legend "HS-1 Universal Grinder" by S. E.Huffman Corporation, South Main St., Clover, S.C., 29710, assignee ofthe present invention. The HS-1 grinder was introduced in 1975 andrelative movement of the grinding wheel and tool with respect to sevenreference axes moving relatively, independently and simultaneously wasachieved. However, while the HS-1 grinder represented a significantadvance in the prior art, it has been found that an even greater numberof reference axes must be moved independently, relatively andsimultaneously in order to achieve the accuracies required in moderntool grinding operations which the HS-1 could not do. Also, the HS-1grinder had limited ability to spin or rotate the A axis because oflimitations of control. This gave limitations on ability to performgrinding of high helix, tapered cutters, ball nose end mills andgrinding of plain diameters. While the HS-1 grinder allowed theworkpiece to spin, this could be achieved only for a limited time and ata limited speed. Thus, it becomes desirable to provide an improvedgrinder as with the present invention, capable of spinning the workpiecewithout such limitations in time and speed to allow grinding operationssuch as grinding of bar stock or for grinding high helix cutters.

The HS-1 grinder also represented an advance over the prior art inproviding a type of coolant system under numerical control. However, theHS-1 grinder coolant system lacked the ability to vary the quantity ofcoolant and basically required the same quantity of coolant to flowwhenever coolant was being directed towards the tool being ground in aparticular grinding operation. The HS-1 grinder has thus demonstrated aneed for greater versatility in the manner in which the coolant can bedirected and controlled with respect to both timing and direction aswell as quantity and in relation to particular phases of the overallgrinding operation. Also of interest to the present invention is thefact that the HS-1 grinder provided a system for compensating for wheelwear based on automatic gauging of the wheel diameter and, whileconsidered, a feedback for numerical control wear correction was notachieved. However, this experience has dictated a need for an improvednumerically controlled wheel wear compensation system which does notrequire wheel gauging during the grinding operation but neverthelessprovides for automatic numerically controlled wheel wear compensation.

In other respects, the HS-1 grinder, as compared to the presentinvention, utilized hardwired controls which were limited to the numberof axis controllable by one control and to moving three axessimultaneously. The type of controls used with the HS-1 grinder did notprovide for storage of programs, memory, use of a CRT tube for programdisplay, editing, or making of tapes, and did not allow for simultaneousmovement of five, six, seven, eight, and up to ten axes simultaneouslyas with the present invention. In the HS-1 grinder control system, itwas not possible, for example, for the grinding wheel to be moved up anddown with reference to the X, Y, and two rotary axes simultaneouslywhich made the grinding of all cutters, and particularly ball nose endmills, complex as compared to the present invention. Full utilization ofthe U axis was limited since movement of the U axis simultaneous withthe A axis could not be achieved.

Therefore, it becomes an object of the present invention to provide agrinding method for grinding cutters, particularly cutting tools,whereby the entire grinding operation may be performed at one stationwith one grinding wheel, with the tool being held in the same workholder throughout the entire grinding operation and with all of thegrinding steps being achieved under automatic numerical control with ahigh degree of repeatable precision. A further object of the inventionis to provide a grinding method which allows the size and type of thecutting tool being ground to be changed without requiring a new machinesetup. A further object is to provide a grinding method that allowsresharpening of cutters to exact tolerance, with speed and ease andunder massive coolant. Another object of the present invention is toprovide a grinding method for grinding a complex workpiece requiringsimultaneous movement of multiple axis including 5, 6, 7, 8, e.g., aball nose end mill, and at the same time allow for automatic wheel wearcompensation and automatic wheel size compensation. A further object isto provide a method wherein the grinding wheel can be trued or dressedusing the simultaneous motion of two or more rotary axes in conjunctionwith simultaneous movement of two or more linear axes. Another object isto provide a grinding machine capable of making a complex workpiececomplete from softened or hardened bar stock. Further, an object is toachieve such a complex workpiece by use of one grinding wheel or by useof multiple grinding wheels on the same end of the wheel spindle or onboth ends of the wheel spindle. The foregoing and other objects willbecome apparent as the description proceeds.

SUMMARY OF THE INVENTION

The grinder employed with the method of the invention is constructed andis operated in reference to the typically fixed X, Y, Z reference axes.The various relative motions and positions of the engaging points on thegrinding wheel and the tool being ground are related to these fixedaxes. Also, the various cutting edges and clearance surfaces aremathematically located and defined with reference to a fixed point whichin turn maintains a fixed relation to the intersection of the fixed X,Y, Z reference axes. Other reference axes are designated X1, Y1, Z1, G,U, V, A, B, and D. Points on the tool are positioned under numericalcontrol relative to five and, alternatively, relative to six referenceaxes. Points on the grinding wheel are positioned under numericalcontrol relative to three and, alternatively, relative to four referenceaxes. Rotation of the tool work holder about reference axis D in oneembodiment is accomplished manually and the position remains fixed, onceset. In an alternative embodiment rotation of the tool work holder aboutreference axis D is accomplished under numerical control. Rotation ofthe entire grinding wheel support system about reference axis Z1 alsopartakes of two embodiments. In one embodiment, such rotation ismanually adjusted and remains fixed, once set. In an alternativeembodiment, such rotation is accomplished under numerical control aspart of an overall programmed operation. The grinding wheel motor axisis reference axis G.

According to the present invention, the cutter tool, a ball nose endmill being used for illustration, is ground at one station underautomatic numerical control such that the end mill once ground is groundcomplete and is ready for use in its intended application. A CNC(computer numerical control) type control is employed in conjunctionwith DC closed loop servo drive systems of the pulse width and frequencymodulated type. All of the edges and surfaces to be ground aremathematically located and defined and during the numerically controlledgrinding operation are generated in reference to an arbitrary fixedpoint which remains fixed with reference to the XYZ intersection andthroughout the grinding operation.

In addition to providing for program control over the grindingoperations, per se, the method of the invention also includes animproved wheel wear compensation program which can be preset formodifying the machine movements when grinding successive tools in orderto adjust for the marginal wear on the grinding wheel which isexperienced from tool to tool. The method of the invention also providefor automatic wheel size compensation. The grinding wheel is of aconstruction which uniquely lends itself to such automatic programmedwheel wear compensation. Thus, the need for operator skill is removedfrom this operation. Additionally, the invention method utilizes amulti-bank coolant supply system having the capability under numericalcontrol of supplying the required lubricant-coolant at selected times,in selected directions, and in selected quantities according to theparticular grinding operation being performed and to properly directmaximum coolant when required.

The tool is completely ground in reference to a fixed point aspreviously stated and the tool itself remains in the same work holder atthe same station and is ground completely with the same grinding wheelto completion. This results not only in a more uniformly ground tool butin a tool which once used and in need of regrinding can be regroundusing the same reference point. Furthermore, all of the ground edges andsurfaces are precisely formed concentric to the tool shank, anachievement not heretofore obtained except possibly at the expense ofgreat time and effort.

In one embodiment, the workpiece, i.e. the tool, and the grinding wheelare automatically moved relative to each other and relative to eightreference axes by numerical controlled servomotor means. In anotherembodiment, ten reference axes are under numerical control. In bothembodiments, the tool and grinding wheel may be moved relatively,independently and simultaneously with respect to as many as eightreference axes. What the invention provides with respect to end millgrinding is the capability of grinding the end gash, secondary and/orradial relief on the end teeth, O.D. relief including primary, secondaryand/or radial relief and the desired rake-angle--positive, negative, orcombination thereof.

The grinding machine includes a workpiece support system that has aquick change adaptor and collet or other means (holding tube) forholding the workpiece. A numerically controlled servomotor arrangementcontrols rotation of the workpiece and indexing, i.e. the tool, aboutits own longitudinal axis, reference axis A. The workpiece supportsystem is mounted on a pair of mutually perpendicular horizontal slideswhose positioning is referenced to reference axes U and V. Theselast-mentioned horizontal slides are, in turn, mounted on a rotary tablewhich revolves around reference axis Z1. The rotary table is mounted onanother horizontal slide whose positioning is referred to reference axisX1. The rotary table and the three horizontal slides are all numericallycontrolled and are independently positioned by the previously describedservomotor drive mechanism.

The grinding wheel has a numerically controlled drive system such thatthe wheel may be rotated at selected times and at selected grindingspeeds according to the grinding operation being performed in theoverall grinding sequence. The grinding wheel and its respective drivesystem are mounted on grinding wheel support system having thecapability of moving the grinding wheel and its associated motor driveby numerical control operated servomotor mechanisms vertically along theZ axis, rotatably on the horizontal B axis and horizontally along the Y1axis. As previously mentioned, the entire grinding wheel support systemcan also be manually rotatively positioned about the Z axis or, in analternative embodiment, may be rotatively positioned about the Z axisunder numerical control. In utilizing the machine and method of theinvention after the required program has been installed in the CNCcontrol, the typical ball nose end mill will be prepared for grindingand will be ground in the following described manner.

First, the operator takes the blank end mill, or the end mill to bereground, and inserts it in a collet or holder which, in turn, isinserted into a tool setting device of a type previously known to andused by those skilled in the art. In this device, the operator sets theend mill for the correct length projection and also sets the end mill ina proper radial position so that the flutes to be ground are properlylocated. The cutter holder in the presetting device is accuratelykeyed--set by a "timing" ring--so that when the holder is removed fromthe setup device with the tool to be ground, the same key way--or"timing" ring--will accurately position the tool in the machineworkpiece holder. Prior to placing the tool in the machine, the operatorplaces the tool in a workpiece holder similar to the one employed on themachine. The tool in which it is now installed is rotated to determinewhether the end mill is running concentric. If not within the limits ofconcentricity set by the standards being followed, then appropriateadjustments can be made to come within those limits. The tool is nextremoved from the test workpiece holder and is placed in the workpieceholder on the grinding machine of the invention. The key way and endstop on the machine workpiece holder accurately locate the end millradially and linearly in relation to the previously mentioned ten axeson the grinding machine and in relation to the grinding wheel itself. Ifnot previously calibrated, the machine can be calibrated by using ablank bar of predetermined dimensions in the machine workpiece holder sothat all slides and rotary elements can be brought to a knownpredetermined starting position under numerical control. Thiscalibration procedure will be apparent to those skilled in the art.

Once the end mill has been prepared for grinding and installed in themachine as described above, all of the positionable elements of themachine are brought to predetermined, initial starting positions. In theembodiment of the invention in which rotative adjustment aroundreference axes D and Z are controlled manually, these adjustments aremade manually and, once fixed, remain set. Otherwise, all of thepositionable elements which are numerically controlled are brought topredetermined positions by a subprogram identified later in thedescription as the "load/unload" program.

Referring next to the purely automatic functions which are performedunder numerical control, the initial operation is directed topositioning the tool for flute grinding and cutting the coolant systemon for flooding a particular quantity of coolant and in a particulardirection as later described in more detail. Also, at this time, thegrinding wheel motor drive is numerically controlled to come on and tooperate at a predetermined optimum speed for the flute grindingoperation. The flutes are then ground into the tool and after being soground provide a precise reference for later grinding operations. Therelative positions, motions and rotations of all slides are dictatedfrom mathematical equations. By this is meant the grinding movements areaccording to mathematical equations converted to numerical control.While the programming of cutter paths and grinding wheel paths hasbecome a known state of the art, reference is made here that in order todevelop the present system, considerable effort has been expended toprogram the use of multiple slides, particularly when using more thanfour axes. These programs have been written manually and also computeraided programs have been developed. These computer programs or executiveprograms or post processors, as the industry has called them, enable thepresent invention to grind simple and complicated shapes with a minimumof programming effort. The method of writing such programs is a knownscience in the industry, both manually and by computer.

Upon completion of the flute grinding operation, all of the numericalcontrolled positionable elements of the machine are positioned for thegash and end teeth relief operation. Next, wheel and tool are positionedfor grinding the primary and secondary or radial relief. After thislast-mentioned operation, all of the numerically controlled positionableelements of the machine retract to their respective start positions, andthe coolant and grinding wheel drive as well as all of the otherservomotor drives are rendered inoperative, after which, the finishedend mill may be removed from the machine and will have been preciselyground for its end use.

Mention should be made here that the described grinding operations areperformed at programmed speeds and feeds and the timing, quantity anddirection of the coolant is also programmed and these variables willperiodically change during the overall grinding operations. Ofparticular significance to the degree of precision obtained by theinvention method and machine is the fact that all of the programmablevariables are controlled not by the operator but by supervisorymanagement such that optimum speeds, timing, feeds, coolant quantity andcoolant direction can all be optimized and independent, simultaneous,incremental movements maximized.

Also to be mentioned, as later described in more detail, is the factthat wheel wear can be predetermined based on experience and thepredicted amount of wear can be placed into the program such that all ofthe affected positions can be changed sequentially to compensate forwheel wear as one tool is finished and before the grinding of anothertool commences. Grinding operations can also be programmed to match suchcharacteristics as wheel diameter, type of wheel, e.g., rough or finish,and the like. For some grinding operations the grinding wheel speed maymount different types of wheels and plural wheels on the same or onopposite ends of the wheel spindle.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a preferred embodiment of the grinding machineof the invention showing the tool in the workpiece holder and thegrinding wheel spaced apart in a nongrinding operation and with variouscomponents of the machine, such as the coolant-lubricant supply,connecting electrical lines and the numerical control itself not beingshown to facilitate illustration of those components which are mostpertinent to the invention, the control being indicated in blockdiagram.

FIG. 2 is an end view of the grinding machine as viewed from the leftside of FIG. 1 with coolant lines removed.

FIG. 3 is a top plan view of the grinding machine illustrated in FIGS. 1and 2.

FIG. 4 is a perspective view of the grinding machine with the workpiecesupport system turned 90 degrees counterclockwise from the positionshown in FIGS. 1, 2 and 3.

FIG. 5 is a block diagram showing the operator functions within theprogrammed numerical control and various programs.

FIG. 6 is a section view of the grinding wheel.

FIG. 7 illustrates typical coolant flow on the wheel and tool forgrinding the gash.

FIG. 8 illustrates typical coolant flow on the wheel and tool forgrinding the flutes.

FIG. 9 schematically illustrates the numerically controlled coolantsystem.

FIG. 10 is a diagram showing the geometric relationship of the designaxes for the wheel support system.

FIG. 11 is a diagram similar to FIG. 10 for the workpiece supportsystem.

FIG. 12 illustrates three types of relief obtainable by the machine andmethod of the invention.

FIG. 13 illustrates the wheel, tool finger relation in a prior artmethod.

FIG. 14 is a schematic view of an alternate grinding wheel arrangement.

FIG. 15 is a schematic view of another alternate grinding wheelarrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings and particularly FIGS. 1-4, there are shownthe basic elements of grinding machine 10 of the present invention. Itshould be understood that none of FIGS. 1-4 show the numerical controlin detail and the legend "To NC" is used to indicate a numericallycontrolled component utilizing a servomotor mechanism as laterdescribed. Also, the coolant system is eliminated in FIGS. 1-4 forpurposes of simplification. FIG. 9 diagramatically illustrates thecooling system; however, it should be understood that, while not shown,the machine and method of the invention do incorporate appropriate meansto recover, filter, pressurize and reuse the particularcoolant-lubricant fluid. Also, various necessary splash covers would beemployed as required though not shown except schematically in FIG. 9.

Machine 10 includes a grinding wheel 12 and the workpiece or tool 13 ismounted in the workpiece holder 15. Grinding wheel 12 is, in turn,mounted on a grinding wheel support system 20 and workpiece holder 15 ismounted on a workpiece support system 30. Systems 20 and 30 are, inturn, mounted on the upper surface of a base table 16.

The grinding wheel support system 20 comprises a vertically movablesupport column 21 whose vertical positioning is numerically controlledin reference to fixed reference axis Z as indicated in the drawings. Anumerically controlled horizontal slide 22 is mounted atop column 21 andwhose horizontal positioning is in reference to offset axis Y1. Agrinding wheel drive motor 24 is rotatably positioned under numericalcontrol in reference to axis B passing through slide 22 and rotatablymounted support member 25. Slide 22, drive motor 24 and rotatablemounting member 25 are all mounted on column 21. Thus, all of theseelements move vertically up and down as the positioning of column 21 isnumerically controlled during the grinding operation by positioner 26.Thus, the vertical location of reference axes B and Y1 may benumerically controlled simultaneous with the numerically controlledlinear positioning of slide 22 and independent of the simultaneousrotative positioning under numerical control of grinding wheel drivemotor 24 about axis B of mounting member 25. Positioning of member 25 iseffected by an associated N/C drive motor 25 and appropriate gear box25" mounted within slide 22 as indicated in FIG. 3. Wheel 12 itselfrotates around reference axis G.

To further explain the versatility in the relative wheel positioning andrelative tool positioning afforded by the present invention, it shouldbe noted that reference axis Y1 represents a horizontal axis parallel tothe X-Y axis plane with respect to which slide 22 can be moved in andout to move the engaging point of grinding wheel 12 on the edge orsurface of tool 13 being ground. The reference axis B also residesparallel to the X-Y axis plane and the relative positioning of drivemotor 24 under numerical control thus provides means for rotating wheel12 relative to axis B. While reference axis B is illustrated asvertically offset above reference axis Y1, reference axis Y-1 andreference B may be designed to coincide and be considered as both alinear and rotary axis. FIG. 4 also indicates other rotative positioningof column 21 with reference to the X-Y plane. Thus, as schematicallyindicated in FIG. 10, any arbitrary reference point P on the cuttingedge of wheel 12 can rotate under numerical control relative to axis B,as indicated by P1, can move longitudinally under numerical control withreference to axis B, as indicated by P2, can be positioned verticallysimultaneously with vertical movement under numerical control of axis B,as indicated by P3, or can be rotated under manual control or,alternatively, under numerical control with reference to axis Z, asindicated by P4.

With respect to the last mentioned rotative positioning of the entirewheel support system about axis Z, it should be noted that the inventionprovides for alternative manual or numerically controlled positioning ofsuch rotation about axis Z. In general, with experience obtained todate, it has been discovered that due to the wide range of N/C axialpositioning afforded by the invention, a wide range of end cutting toolscan be ground with the degree of precision contemplated if rotation ofthe vertical wheel support structure provided by column 21 about axis Zis within a range of plus or minus forty-five degrees from a centralposition and accommodation is made for fixing such rotated position foreach particular tool being ground. However, it is also contemplated thata desire for even higher degrees of precision and even more complexgrinds than those found in a ball nose end mill will be sought in thefuture making use of the present invention. Thus, provision is also madefor rotation of the wheel support structure, i.e. column 21, about axisZ under numerical control. Collar 27 thus has a vertical slidableengagement with column 21 and is also adapted to either manualpositioning as indicated by manual tightening knob 28 or by anappropriate N/C drive 29 appropriately internally geared to collar 27.

Since the general construction of numerically controlled slides androtary elements are known to those skilled in the art, the details ofthe slides, servo mechanisms and the various mechanical elementsassociated with the described rotary and linear positioning movementsare not shown in detail. In a preferred embodiment, the servomotor drivesystems of the invention preferably employ DC closed loop servo drivesystems and which are further identified as being of the pulse width andfrequency modulated type such as sold by Control Systems Research, Inc.,1811 Main St. Pittsburgh, Pa., 15215. Such a servo drive system offersnot only precision positioning but also enables the workpiece to spinwithin a wide speed range and for long time intervals. Thus, bar stockgrinding, high helix cutter grinding and like operations can beaccommodated as well as the incremental grinding of complex edges andsurfaces.

It may also be mentioned here that a preferred type of numerical controlis the CNC, i.e. Computerized Numerical Control, type illustrated by thesystem 7320 Series, sold by the Allen-Bradley Company of HighlandHeights, Ohio, 44143. Those skilled in the art will appreciate that theCNC type of control offers unique advantages over hardwired andparticularly in regard to providing the possibility of moving as many aseight and possibly 10 reference axes simultaneously under numericalcontrol, since it has been discovered that it is this ability of thepresent method and invention apparatus to move such a large number ofaxes simultaneously that leads to the long desired degrees of precisionwhich were not previously obtainable. Other programmable, incrementaltype controls and incremental drive members equivalent to N/C andservo-drives could be employed.

Having mentioned the type of servomotor drive systems and type ofnumerical control which are preferred to obtain the degrees of precisionsought by the invention, other features of construction are also deemedimportant to the obtaining of such precision. For example, ball screwdrives are used for all of the linear motions. The rotary motions aredriven by helical gears and are designed to give virtually no backlash.All of the bearings employed are selected to provide preload adjustment.Thus, the machine and method of the invention, when built and operatedas described, enables the obtaining of a tolerance of better than 0.001inch as compared to the typical prior art tolerance of greater than0.001. Concentricity and run out within 0.0002 inch can be achievedwhere prior art could be as much as 0.004 and more.

Having described the general construction and the overall arrangement ofthe grinding wheel support system 20, the description will next refer tothe workpiece, i.e. the tool, support system 30.

In this regard, workpiece support system 30 includes five andalternatively six numerically controlled, servo-driven mechanisms. A N/Chorizontal base slide 31 is horizontally positioned in reference to axisX1 which resides parallel to axis X and parallel to the XY plane. Slide31 is operated by means of an associated drive shaft 31', a gear box 31"and N/C drive motor 31'" which are suspended on, below and travel withslide 31. A N/C rotary table 32 mounts on slide 31 and rotates relativethereto in a "c" rotation in a horizontal plane and about verticaloffset axis Z1. A N/C horizontal slide 33 mounts on and rotates withtable 32 and is horizontally positioned in reference to axis U whichresides parallel to the XY plane. A N/C horizontal slide 34 mounts onand rotates with horizontal slide 33 and is horizontally positioned inreference to axis V which resides normal to axis U and parallel to theXY plane. Workpiece holder 15 mounts in saddle 36 which, in turn, issecured to horizontal slide 34. Saddle 36 provides a pivotal mountaround reference axis D for workpiece holder 15. Reference axis D isnormal to the tool axis A. A suitable N/C drive means 35 mounts onworkpiece holder 15 and is adapted to rotate the workpiece, i.e. thetool, about its longitudinal axis, reference axis A.

Pivoting of workpiece holder 15 within a range of plus or minus 20degrees about reference axis D may be accomplished manually with anappropriate manual knob 37 or through an appropriate optionalnumerically controlled drive means 38. In this regard, it has beendiscovered that in view of the high degree of precise N/C positioningafforded by the machine and method of the invention that the rotativepositioning of workpiece holder 15 around reference axis D can normallybe manually fixed within a range of plus or minus twenty degrees from aneutral position by use of manual adjustment knob 37 and held therethroughout the grinding. However, as with rotative positioning of thewheel support system around axis Z, as previously explained, it iscontemplated as more complex grinds are defined in the future and as analternative form of positioning to provide a N/C drive motor 38 suchthat rotative positioning of holder 15 around axis D may also benumerically controlled and be subject to precise, incremental,independent and simultaneous positioning with respect to all other N/Cdrives and while the grinding sequence is proceeding. Thus, when bothN/C rotary drive 29 for positioning around axis Z and N/C rotary drive38 for positioning around axis D are employed, the machine and method ofthe invention provides the possibility of ten N/C axes and with the N/Cdrive for each of such ten axes being adapted for incremental,independent and simultaneous positioning.

As can be seen from the foregoing description and the accompanyingdrawings, slide 31 provides horizontal motion in the X1 axis directionunder numerical control and supports rotary table 32 and the remainderof the elements of the support system 30 above table 32. Since rotarytable 32 is mounted on and directly above slide 31, table 32 can movehorizontally with slide 31. Rotary table 32 by rotating relative toslide 31 is also designed to support and impart rotary motion aroundvertical Z-1 under numerical control to those elements residing aboverotary table 32, that is, to slides 33, 34, saddle 36 and workpieceholder 15. Slide 33 should also be noted as being adapted to rotate withrotary table 32 and under separate numerical control being adapted toprovide horizontal displacement along the U axis. The independently andseparately numerically controlled slide 34 which mounts on slide 33provides displacement along the horizontal reference axis V which isnormal to the reference axis U, as shown.

With the immediate foregoing description in mind and referring to FIG.11, it will be noted that any arbitrary point P' can be rotativelypositioned around axis A by the numerically controlled drive means 35,can be caused to move along axis A by the numerically controlled slide33, can be caused to move along an axis perpendicular to axis A byoperation of numerically controlled slide 34, can be caused to rotatearound axis Z-1 by numerically controlled rotary table 32 or can becaused to rotate around reference axis D by operation of the manualadjustment knob 36 or optionally, by operation of the numerical control38 which under the optional arrangement enables the numericallycontrolled positioning of point P' with reference to axis D. Aspreviously explained, this last arrangement in conjunction with use ofoptional N/C drive 29 provides a maximum of ten N/C axes. Particularnote should be taken that the numerically controlled servo drivemechanisms which operate slide 31, rotary table 32, slide 33, slide 34,drive means 35 and, optionally, drive means 38 are all adapted tooperate completely independently and simultaneously thus enabling theobtaining of an extremely high degree of precision not heretoforeobtained in any known numerically controlled end mill grinding apparatusor method. Also to be noted in conjunction with the highly versatilepositioning capability of the tool itself is the equally importantpositioning capability of the grinding wheel and its related supportsystem 20 as previously described. Thus, overall, the machine and methodof the invention provides an extremely versatile positioning capabilitynot heretofore achieved in any known prior art machine or method.

One of the advantages of the present invention resides in the fact thatall the grinding operations can be completed utilizing a coolant andavoiding the dry grinding method of the prior art which had manydisadvantages as previously explained. While it was known prior to thepresent invention to provide a coolant supply under numerical control ina grinding operation, the numerically controlled coolant supply systemsof the prior art, so far as is known, called for the coolant supply when"on" to be limited to a specific quantity of coolant being directed tothe grinding area in a specific quantity. Such prior art systems did notprovide for controlling the quantity of coolant by a numericallycontrolled system nor did the prior art systems allow the direction offlow of the coolant to be regulated under numerical control. On theother hand, it is known that certain grinding operations are betterperformed with less coolant than other grinding operations. It is alsoknown that since the angle of attack of the grinding wheel towards thetool being ground is substantially different in one grinding operationthan in another grinding operation and the actual area being ground willvary substantially from one operation to another operation, it is alsoknown that the direction in which the coolant is directed towards thegrinding area can be optimized for each grinding operation. With theforegoing in mind, the present invention provides means for numericallycontrolling both the quantity of coolant and the direction ororientation of the coolant flow according to optimized conditionsrelated to the particular grinding operation being performed. FIGS. 7and 8 illustrate typical situations.

A somewhat schematic diagram of the coolant system is illustrated inFIG. 9. The coolant is collected, recirculated and reused throughappropriate piping 39, collection basin means 42, and the like, ofconventional construction and which are not otherwise shown in detailfor purposes of simplification. The coolant is transferred through anappropriate pump 41 and is held in a suitable pressurized storage vessel40 for transfer to a multi-coolant bank 43 through a pair of numericallycontrolled valves 44, 45. As indicated in FIG. 9, coolant bank 43comprises respective upper and lower dispensing chambers 46, 47.Chambers 46, 47 are thus designed to independently supply coolant to thegrinding area through respective independent sets of coolant dischargelines 48, 49. Thus, the coolant may be supplied through either or bothof discharge line sets 48, 49 so as to apply coolant to the grindingoperation in the appropriate quantity and in the appropriate orientationor direction as required for optimizing the particular grindingoperation. Discharge lines 48, 49 may be made either of a rigid tubing,e.g. copper, and bent so as to assume a fixed direction of discharge andso that lines 48 assume one direction of orientation and lines 49 assumea different orientation or lines 48, 49 may be formed of a type oftubing which can be bent to a particular shape as required such as usedwith flexible oil funnels, and the like, thus allowing coordination ofcoolant with grinds as in FIGS. 7-8 and some freedom in changing thedirection of discharge with the type of tool being ground. Where thesame type of tool is being ground on a repetitive basis, it is, ofcourse, contemplated that lines 48, 49 will have their respectivedirectional orientation fixed for grinding that particular type of toolunder optimum conditions. It is also contemplated that where sufficientwork is available for repetitive grinding of a single type of tool thatthe prior art method of providing a fixed quantity of coolant which isalways supplied in the same orientation and in the same quantity will beadequate and such prior art method of operating the coolant supply is,of course, compatible with the other features of the invention hereindisclosed.

A coolant program is made a part of the overall computerized numericalprogram control as indicated in FIG. 5. Thus, the program itself can bereadily changed to vary the specific manner in which the coolant issupplied to optimize such coolant supply for a particular operation on aparticular type of tool. The adaptability of the invention to use of acoolant in the manner described is, of course, highly desirable since itserves to reduce friction and wear on the grinding wheel and alsoprovides a superior surface finish on the completed cutting tool. Theinvention is deemed particularly advantageous in not only eliminatingthe frequently used and inherently dry grinding process of the prior artbut is providing a unique means for optimizing the manner in which thecoolant is supplied in the grinding operation and without resort tooperator skill.

As previously mentioned, the various automatic and numericallycontrolled motions of machine 10 are designed to enable the grindingwheel 12 and workpiece 13 to be brought into operative engagement witheach other at virtually any desired angular relation necessary for thegrinding of cutting tools. As shown in the block diagram of FIG. 5, thegrinding operations involved in the grinding of a ball nose end millincludes: helix or flute grinding including the gash to center, primaryand secondary relief angles on end teeth, (the radius), and the primaryand secondary O.D. relief. What should be observed here is the fact thatthe grinding wheel edge will undergo a certain amount of wear in thecourse of completing the grinding operations on each end mill. Thus, itbecomes necessary to compensate for this wear in order to maintain thedesired degree of precision from one ground tool to the next. In thepast, with manual adjustments, such wear wheel was compensated forthrough operator skill and experience. Thus, one operator's ability andexperience might dictate one amount of compensation whereas anotheroperator's ability and experience would dictate another amount ofcompensation which led to substantial nonuniformity as between toolsground by one operator as compared to tools ground by another operator.The previously-mentioned practice of providing means to automaticallygauge the grinding wheel after completion of grinding of each tool andthe operator adjusting by numerical control by manual input representedan advance over the purely manual wheel compensation method butnevertheless still required the complexity of the gauging and operatorinput. The present invention has sought to offer a dramatic improvementover the manual wheel wear compensation method and even a significantimprovement over the known prior numerically controlled wheel wearcompensation methods.

In connection with the present invention, it has been discovered thatthe amount of wheel wear can be predicted with sufficient accuracy toallow programming of fixed amounts of wheel wear compensation so thatrelative positioning of the grinding wheel and the tool being ground canbe adjusted from tool-to-tool or even within one tool with sufficientaccuracy to maintain a high degree of tolerance to compensate forgrinding wheel wear. This discovery is based on discovering that if thegrinding wheel itself is made according to a particular form and if thegrinding wheel is repetitively used under precise numerically controlledand optimized conditions that the amount of wear can be madesufficiently uniform to allow sufficiently precise wheel wearcompensation under program control to insure a relatively high degree ofprecision. The present invention, in its preferred form, is based uponusing a grinding wheel which is so made that it can be used throughoutall of the grinding operations required on the typical end mill andfurther is designed so that when the manner in which it is used isprecisely numerically controlled the wear rate can be made substantiallyuniform and compensated for by programming alone without requiring anymanual adjustment on the part of the operator and without requiring anyof the relatively complex wheel gauging and feedback arrangements knownto the prior art wheel wear compensation systems.

More particularly, it has been found that the amount of compensationrequired can be determined through experience and measurement withsufficient precision of the estimated wear on the wheel edge caused bythe grinding of each tool to allow this information to be translated ascontrol information in the numerical control program. After the grindingof each tool, the wheel wear compensation program thus automaticallyprograms the appropriate servomotor mechanisms controlling the elementsof wheel support system 20 and workpiece support system 30 to move eachof the respective axes of the grinding wheel and the workpiece slightlycloser together to compensate for wheel wear. Once so programmed, itwill be appreciated that no feedback or wheel gauging is thereafternecessary. In the grinding of a typical ball nose end mill, as anexample, and with the preferred grinding wheel utilized in the presentinvention, a wheel wear of approximately 0.001 inch is typical nominalvalue for the wear to be expected from the grinding of each tool on theedge that actually performs the grinding. The wheel wear compensationprogram does not necessarily require that such compensation be madeafter the grinding of every tool but when tolerances so allow may bemade, for example, after a set of tools have been ground such as a setof five tools. As noted, each wheel wear compensation program willinclude a nominal value expected to be the average wear per cutting toolgrind. If the actual wear varies from the estimated nominal value, theprogram may be readily modified. For example, it has been found that newgrinding wheels may wear somewhat less than the estimated amount whereasworn wheels with a remaining useful life may wear somewhat more than theestimated amount. As noted in FIG. 5, a manual adjustment for the wheelwear compensation is provided for the purposes just described. Thus, ifby actual observation or measurement of the workpiece, a particularwheel requires more or less compensation than has been programmed, suchadjustment can be made within the control by the operator manuallyselecting a different set of values from stored memory. The control thenadjusts the program output itself as required. Thus, as an example, if atool being ground due to heat treating has been made of harder metalthan the tool blank previously ground, there will be more wear on thegrinding wheel due to the harder metal and the necessary wheel wearcompensation correction can be made very rapidly in the mannerdescribed.

The type and shape of grinding wheel utilized for practicing theinvention is deemed important, however, most any feasible shape could beused depending on the product to be ground, because of the multipleslides and the relative positions obtainable with them. One preferredgrinding wheel 12 is shown in FIG. 6. It will be noted that grinidingwheel 12 partakes generally of a known saucer shape in cross section andis provided with a diamond grinding face insert 50 which, in the formillustrated, is designed to wear back evenly during the life of thegrinding wheel. In one embodiment, the coolant was sulphurized chlorideoil, the wheel had a diamond edge and the tool had tungsten carbidesurfaces. Vitrified grinding wheels and water soluble coolants can beused since the wheel wear compensation is so readily adjustable to anyconditions. In one example, the illustrated grinding wheel was designedto wear to the point of reducing the diameter by one-half inch before itbecame necessary to discard the wheel. Note should be taken here thatuniform wheel wear not only extends the useful life of the wheel but itreduces any adjustment to the operation of the wheel wear compensationprogram. Also, by controlling the manner of wheel construction andprecisely controlling its positioning during use under numericalcontrol, an important objective of the invention is achieved, namelythat of being able to completely grind the tool at one station with thesame grinding wheel being used for all of the grinding operations.

While previously mentioned, it should be recognized that while thepresent description is primarily concerned with ball nose end millgrinding with a single wheel, other applications may employ automaticcompensation for wheel size as well as wheel wear. Also, as laterdescribed, wheels of different shape may be employed on the same oropposite ends of the spindle. Also, the invention allows for trueing ordressing the grinding wheel itself when so required.

Another feature of the program control illustrated in FIG. 5 is thegrinding wheel speed program. In this regard, it is long been known thatthe grinding of particular edges or surfaces are better performed at onewheel grinding speed than another. Therefore, for the purpose ofoptimizing grinding wheel speed according to the grinding operationbeing performed, the grinding wheel drive motor 24 is provided as avariable speed motor and the grinding wheel speed program indicated inFIG. 5 is thus enabled to control the rotational speed of grinding wheel12 such that for optimum grinding conditions, the grinding wheel 12 willrotate at the particular speeds which are appropriate to the particulargrinding operations.

It will also be appreciated that when wheel support system 20 andworkpiece support system 30 are being repositioned after completing onegrinding operation and before commencing another grinding operation, itmay be desirable to stop and restart the rotation of the grinding wheel12. For this purpose, as indicated in FIG. 5, there is also providedwhat is designated as a "Stop/Start Program". It will, of course, beappreciated that not all transitions between grinding operations willrequire that the rotation of grinding wheel 12 come to a complete stop.In these circumstances, the Stop/Start Program would be ineffective.

To complete the description of FIG. 5, it will also be noted that aso-called "Load/Unload Program" is provided and this program is designedto bring the respective wheel support system 20 and workpiece supportsystem 30 to their respective programmed starting positions each time agrinding operation is completed on a particular tool in order that suchground tool may be removed from the machine and a new tool loaded intothe workpiece holder 15 in the manner previously described. Appropriatemanual override controls may be provided for emergencies, unexpectedcircumstances, and the like, as generally depicted in FIG. 5 and whichmay be arranged according to well-known practices in the art.

As illustrated in FIG. 4, grinding machine 10 is adapted for rotativepositioning about reference axis D and also for rotative positioningabout reference axis Z. Mention has also been made that rotation aboutthe respective reference axes D and Z may be obtained manually and fixedmanually or, in the optional arrangement indicated, may be positionedand fixed manually by numerical control as indicated. In either event,prior to commencing the grinding operation, it is contemplated that theworkpiece holder 15 will be rotated about reference axis D through anangle of plus or minus twenty degrees from the horizontal and will thenbe locked into such position by means of an appropriate locking means.Also, it is contemplated that the rotational positioning about axis Zwill allow a movement of plus or minus forty-five degrees from a centralposition and this rotational position will also be made and fixed beforethe grinding operation commences. The reason that reference axis D andreference axis Z are rotatively positioned and fixed is that it has beenfound that all of the necessary grinding operations on the typical endmill, and particularly the ball nose type end mill being used as anexample, can be completed by initially locking workpiece holder 15 in afixed rotative position around axis D and by locking column 21 and allof the supported structure thereon in a fixed rotative position aboutaxis Z since further controlled rotative movement of reference axis Dand further controlled rotative movement of column 21 about axis Z willnot thereafter be required. Optionally, N/C drives 29 and 38 are used.

In a preferred mode of operating machine 10, the workpiece 13 is placedin the workpiece holder 15 and the Load/Unload Program brings therespective wheel support system and workpiece support system 30 to theirrespective starting positions as will have been previously calibratedand determined. Using the grinding of a ball nose end mill as an examplein the preferred program operation, prior to commencing of any grinding,a selected arbitrary point on the tip end of the workpiece 13 will beinitially positioned in a definite relationship with the startingpositions of all of the reference axes of the machine. Here note mightbe taken that the grinding operation now scheduled to commence willbasically consist of generating the required edges and clearancesurfaces on the tool 13 in the manner required. What should also beunderstood is that each of the edge and surface grinding programsindicated in FIG. 5 represent precise programs for mathematicallylocating all of the edges and clearance surfaces to be ground during theoverall grinding operation.

With the above in view, the first grinding operation involves theestablishment of a geometric mathematically-defined helical cuttingsurface which is accomplished by grinding a helical shape into the toolaccording to the mathematically-generated helix grinding program storedin the computer control. After completion of the helix which will alsohave resulted in grinding the correct rake in the flutes, the respectivewheel support system 20 and workpiece support system 30 will berepositioned to grind the necessary relief angle. The gash, primary andsecondary relief angles on the end teeth will be ground sequentiallyfollowed by grinding of the radius and chamfer on the corners and,finally, grinding of the primary and secondary O.D. relief. Throughoutthese various operations, it will, of course, be understood that thecoolant program will be numerically controlled to come on and off asrequired and to vary the quantity of coolant as previously explained.Also, the grinding wheel speed program will numerically control thespeed of the grinding wheel 12 as required and the rotation of grindingwheel 12 will be stopped and started during the grinding operation bythe Stop/Start Program as previously explained. At the end of thecomplete grinding operation, the tool will have been completely groundand will be ready for its intended application. Also to be noted is thatthe grinding operation can be programmed for special geometric shapes,e.g. radius ball nose cutters, tapered cutters, hollow, flat and radialreliefs, and the like, such that the finish tool will include anydesired special geometric shape in addition to the ordinary tool shapeor any of the reliefs shown in FIG. 12.

While the description thus far has dealt principally with application ofthe invention to grinding of a ball nose end mill, other applications,features, and uses of the invention should be recognized. For example,the unique arrangement of the various reference axis, the availabilityof the relatively large number of N/C simultaneous movements and theability of the grinding wheel to spin on axis B gives wide latitude inapplication of the invention. For example, it can be seen as previouslymentioned that machine parts such as hydraulic valve spools, cams, crushform dressing rolls, and the like, can be ground quickly and with a highdegree of precision according to programs fitting the respective parts.The grinding wheel itself can be trued or dressed by mounting the wheelas the "workpiece" and grinding the same with an appropriate dressingwheel. In this operation, two N/C rotary and two N/C linear axes couldbe used simultaneously to facilitate the operation. As illustrated inFIG. 14, by way of example, the invention facilitates use of multiplewheels and there is shown a rough grind wheel 60 and a finish grindwheel 61 on one end of the spindle 70 and a wheel of larger diameter 62on the opposite end of the spindle and which would be available for anyother grind suited to the job in hand. As further illustrated in FIG.15, a wheel 65 of one shape could be mounted on one end of the spindle70 and a wheel 66 of different shape could be mounted on an opposite endof spindle 70 and either could be oriented as required under numericalcontrols as previously described. Engraving operations are also entirelyfeasible.

In summary, the grinding machine and method of the present inventionafford a number of advantages over the prior art. In particular, thecutting tools may be ground with no heat cracks, better surfacefinishes, more accurate indexing of the cutting edges, more accurate runout, and with precisely repeatable geometry. A choice of reliefsincluding hollow ground, flat ground and radial is afforded.Resharpening of worn cutters is facilitated because the tool can berelocated in the machine in the precise location required to repeat themathematically located and defined geometry of the tool as originallyground. Since all of the grinding is done while the shank of theworkpiece is clamped in one workpiece holder and is ground throughoutwith the same grinding wheel, tolerances of better than 0.001 inch canbe achieved as compared to present tolerances in the range of 0.004 inchwith respect to such dimensions as run out, tooth-to-tooth spacing andO.D. The absence of heat cracks and the improved surface finish areparticularly important and are attributable to the fact that the cuttersare ground with the machine and method of the invention while using acoolant whose flow is under numerical control, while performing allgrinding operations with optimized grinding wheel speeds and whilepositioning both the grinding wheel and tool being ground according topredetermined, precise mathematical formulas which precisely define andlocate the various edges and surfaces ground on the tool. The dry,finger method of FIG. 13 is avoided.

Another advantage which will be appreciated by those skilled in the artfrom the foregoing description is the fact that the machine and methodof the invention leads to a substantial reduction in the setup timerequired for each operation. The usual setup requires skilledworkmanship, is time consuming and must be done for each operation. Inthe grinding of a ball nose end mill, for example, where three separatesetups are required, typical setup times would be one to one andone-half hours for the gasher, one to one and one-half hours for thereliever and one-half to one hour for the radius O.D. In contrast, thetool to be ground with the present method and machine of the inventioncan be set in its adapter and properly adjusted in about two minutes. Onthe infrequent occasions when a new grinding wheel must be replaced,about ten minutes is required. Alternately, instead of a new controltape corresponding to a new tool, this could have been stored in memoryand thus recalled from memory and no new tape would be needed to bringto a operable control condition. Therefore, the total setup time willvary from three to thirteen minutes as compared to two and one-half tofour hours. While the machine and method of the invention are primarilydirected to grinding tools requiring an extremely high degree ofprecision, it is recognized that certain tools of relatively lowprecision, e.g. wood cutting tools, may also be ground according to theinvention but without necessarily requiring use of N/C coolant, anycoolant or the same degree of precision as previously described.Irrespective of the material being ground, e.g., aluminum, steel,plastic, or the part being ground, e.g., soft bar stock or a hard endmill surface, or the wheel being used for the grinding, it can be seenthat the grinding operation conditions can be optimized and programmedto achieve degrees of precisions never heretofore achieved. Suchprogramming, as previously stated, could be by the described N/C or byan equivalent, programmable control and incremental drive and "N/C" isused in this sense.

What is claimed is:
 1. The method of machine grinding a workpiece suchas a cutting tool with a grinding wheel comprising the steps:(a)installing the workpiece in the workpiece holder of the machine andpositioning the central axis of the workpiece with respect to fixedreference X, Y, Z axes appropriate to the first grinding operation to beperformed thereon and fixing the workpiece in such position; (b)incrementally and independently and by N/C, positioning the workpieceduring grinding thereof relative to the following axis:(i) rotatively,with respect to an axis extending through the workpiece as a first axis;(ii) linearly, with respect to a second horizontal linear axis at alltimes disposed below said workpiece axis and fixed perpendicularthereto; (iii) linearly, with respect to a third horizontal linear axisat all times disposed below said second axis and fixed relative thereto;(iv) rotatably, with respect to a fourth vertical axis intersecting saidthird axis and perpendicular to said second axis; and (v) linearly, withrespect to a fifth horizontal axis intersected by and perpendicular tosaid fourth vertical axis; (c) installing the wheel on the spindle of amotor drive supported by the wheel support structure and positioningsaid wheel support structure around a sixth fixed vertical axis to arotated wheel support structure position appropriate to the grinding tobe performed and fixing said wheel support structure in such positionwith respect to rotation about said sixth axis; and (d) incrementallyand independently and by N/C positioning the wheel during grinding ofsaid workpiece relative to the following axes passing through said wheelsupport structure:(i) linearly, in a vertical direction with respect tosaid sixth vertical axis; (ii) linearly, in a horizontal traverse, withrespect to a seventh horizontal axis intersecting and perpendicular tosaid sixth axis; and (iii) rotatively, in a vertical sweep, with respectto an eighth horizontal axis parallel to said seventh axis; and (e)synchronizing said N/C workpiece and wheel positioning by N/C programswhereby said N/C positioning with respect to any number of said axes maytake place simultaneously as and when required during the grinding ofsaid workpiece.
 2. The method of claim 1 including the step of flowing acoolant onto said workpiece during grinding thereof and programming thetiming and volume of said coolant by N/C according to the grinds beingexecuted on said workpiece.
 3. The method of claim 1 including the stepof adjusting the position of said workpiece and wheel by N/C at selectedtimes corresponding to a selected number of workpieces such as toolsbeing ground to compensate for wheel wear and according to a predictedamount of wear per workpiece.
 4. The method of claim 1 including thestep of flowing a coolant onto said workpiece during grinding thereofand programming the timing and volume of said coolant by N/C accordingto the grinds being executed on said workpiece and including the step ofadjusting the position of said workpiece and wheel by N/C at selectedtimes corresponding to a selected number of workpieces such as toolsbeing ground to compensate for wheel wear and according to a predictedamount of wear per workpiece.
 5. The method of claim 1 wherein saidworkpiece comprises a cutting tool and said wheel is formed in a manneradapted to complete the grinding of said tool ready for its intendedapplication by following said steps in an interrupted continuoussequence while said tool remains in the same said holder and all saidgrinding is performed solely with said wheel.
 6. The method of claim 1wherein said workpiece comprises a worn grinding wheel to be dressed andsaid first mentioned wheel is adapted to complete the dressing of saidworn grinding wheel and said programmed machine control is designed toaffect the dressing of such worn grinding wheel and later accept thesame as said first mentioned wheel and compensated for such dressing. 7.The method of machine grinding a workpiece such as a cutting tool with agrinding wheel under program control comprising the steps:(a) installingthe workpiece in the workpiece holder of the machine and positioning thecentral axis of the workpiece with respect to fixed reference X, Y, Zaxes appropriate to the first grinding operation to be performed thereonand fixing the workpiece in such position; (b) incrementally andindependently and by program controlled incremental operator meanspositioning the workpiece during grinding thereof relative to thefollowing axis:(i) rotatively, with respect to an axis extending throughthe workpiece as a first axis; (ii) linearly, with respect to a secondhorizontal linear axis at all times disposed below said workpiece axisand fixed perpendicular thereto; (iii) linearly, with respect to a thirdhorizontal linear axis at all times disposed below said second axis andfixed relative thereto; (iv) rotatably, with respect to a fourthvertical axis intersecting said third axis and perpendicular to saidsecond axis; and (v) linearly, with respect to a fifth horizontal axisintersected by and perpendicular to said fourth vertical axis; (c)installing the wheel on the spindle of a motor drive supported by thewheel support structure and positioning said wheel support structurearound a sixth fixed vertical axis to a rotated wheel support structureposition appropriate to the grinding to be performed and fixing saidwheel support structure in such position with respect to rotation aboutsaid sixth axis; and (d) incrementally and independently and by programcontrolled incremental operator means positioning the wheel duringgrinding of said workpiece relative to the following axes passingthrough said wheel support structure:(i) linearly, in a verticaldirection with respect to said sixth vertical axis; (ii) linearly, in ahorizontal traverse, with respect to a seventh horizontal axisintersecting and perpendicular to said sixth axis; and (iii) rotatively,in a vertical sweep, with respect to an eighth horizontal axis parallelto said seventh axis; and (e) synchronizing said workpiece and wheelpositioning by programmed machine control adapted to control saidincremental operator means whereby said incremental operator positioningwith respect to any number of said axes may take place simultaneously asand when required during the grinding of said workpiece.